| Year | Value | | 2022 | 1.3287223278649 | | 2021 | 1.2899226530826 | | 2020 | 1.7001781609242 | | 2019 | 1.7390701591985 | | 2018 | 1.9557868098796 | | 2017 | 2.5079828055058 | | 2016 | 2.7333349446512 | | 2015 | 3.1054262930828 | | 2014 | 4.6984545156441 | | 2013 | 4.4552394215511 | | 2012 | 3.2366594992165 | | 2011 | 3.2556603512938 | | 2010 | 4.1775845224338 | | 2009 | 4.7096100483207 | | 2008 | 3.5731203806271 | | 2007 | 3.1140544929574 | | 2006 | 3.7614953054353 | | 2005 | 3.6922409469853 | | 2004 | 3.4711801867278 | | 2003 | 3.7614790735473 | | 2002 | 2.8699324451257 | | 2001 | 4.5243538152146 | | 2000 | 6.392603154274 | | 1999 | 17.334692213616 | | 1998 | 2.642011881063 | | 1997 | 5.972268207195 | | 1996 | 2.4478481567171 | | 1995 | 4.7073927682623 | | 1994 | 5.709280690836 | | 1993 | 17.522589075574 | | 1992 | 5.6828305425814 | | 1991 | 7.1025 | | 1990 | 17.463666666667 | | 1989 | 19.432333333333 | | 1988 | 21.9805 | | 1987 | 22.25 | | 1986 | 1.73E-5 | | 1985 | 1.715E-5 |
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